Light-emitting device

ABSTRACT

A light-emitting device is provided. The light-emitting device comprises: an epitaxial structure comprising a first DBR stack, a light-emitting stack and a second DBR stack and a contact layer in sequence; an electrode on the epitaxial structure; a current blocking layer between the contact layer and the electrode; a first opening formed in the current blocking layer; and a second opening formed in the electrode and within the first opening; wherein a part of the electrode fills in the first opening and contacts the contact layer.

REFERENCE TO RELATED APPLICATION

This application is a continuation application of copending U.S. patentapplication Ser. No. 15/062,995 filed on Mar. 7, 2016, entitled as“LIGHT-EMITTING DEVICE”. The disclosure of the reference cited herein isincorporated by reference in its entirety.

TECHNICAL FIELD

The disclosure related to a light0emitting device, and particularly to alight-emitting device having lase and light-emitting diode (LED)characteristic.

DESCRIPTION OF BACKGROUND ART

Light-emitting diodes (LEDs) are widely used as solid-state lightsources. Compared to conventional incandescent light lamps orfluorescent light tubes, LEDs have advantages such as lower powerconsumption and longer lifetime, and therefore LEDs gradually replacethe conventional light sources and are applied to various fields such astraffic lights, back light modules, street lighting, and biomedicaldevice.

FIG. 24 is a cross-sectional diagram showing a conventional verticalcavity surface emitting laser (VCSEL). A vertical cavity surfaceemitting laser (VCSEL) is capable of emitting coherent light in adirection perpendicular to an active region. VCSEL comprises a structurehaving a substrate 300, a pair of DBR stacks 200, 210 on the substrate300 interposing an active region 230 where electrons and holes combineto generate light. A first electrode 240 and a second electrode 250 areprovided for an electrical current to be injected into the active regionto generate light, and the light is exited from an aperture on an uppersurface of the VCSEL.

The vertical cavity surface emitting laser may have an undercut aperture260 in one of the DBR stacks 210. The undercut aperture 260 is formed byselectively etched away a periphery part of one of layers in the DBRstack 210, and thus an air gap having relatively low conductivitycompared to the conductivity of the other layers is formed in the DBRstack 210.

SUMMARY OF THE INVENTION

The present disclosure provides a light-emitting device. Thelight-emitting device comprises: an epitaxial structure comprising afirst DBR stack, a light-emitting stack and a second DBR stack and acontact layer in sequence; an electrode on the epitaxial structure; acurrent blocking layer between the contact layer and the electrode; afirst opening formed in the current blocking layer; and a second openingformed in the electrode and within the first opening; wherein a part ofthe electrode fills in the first opening and contacts the contact layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisdisclosure will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a top view of the first embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 1B is a cross-sectional diagram along an A-A′ line showing thefirst embodiment of the light-emitting device shown in FIG. 1A;

FIG. 2 shows a relationship curve of optical output power vs. forwardcurrent of the first embodiment of the light-emitting device;

FIG. 3A through FIG. 4B demonstrate the method for manufacturing thelight-emitting device shown in FIG. 1A and FIG. 1B;

FIG. 5A is a top view of the second embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 5B is a cross-sectional diagram along an A-A′ line of thelight-emitting device shown in FIG. 5A;

FIG. 6 is a cross-sectional diagram showing the third embodiment of thelight-emitting device in accordance with the present disclosure;

FIG. 7 is a cross-sectional diagram showing the fourth embodiment of thelight-emitting device in accordance with the present disclosure;

FIG. 8A is a top view of the fifth embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 8B is a cross-sectional diagram along an A-A′ line of thelight-emitting device shown in FIG. 8A;

FIG. 9A is a top view of the sixth embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 9B is a cross-sectional diagram along an A-A′ line of thelight-emitting device shown in FIG. 9A;

FIG. 10A is a top view of the current blocking layer of the sixthembodiment of the light-emitting device shown in FIG. 9A;

FIG. 10B shows a cross-sectional diagram along an A-A′ line of thelight-emitting device shown in FIG. 10A;

FIG. 11A is a top view of the seventh embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 11B is a cross-sectional diagram along an A-A′ line of thelight-emitting device shown in FIG. 11A;

FIG. 12A shows a relationship curve of optical output power vs. forwardcurrent of the seventh embodiment of the light-emitting device;

FIG. 12B shows an enlarged detail of region I in FIG. 12A;

FIG. 13A through FIG. 16B demonstrate the method for manufacturing thelight-emitting device shown in FIG. 11A and FIG. 11B;

FIG. 17A is a top view of the eighth embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 17B is a cross-sectional diagram along an A-A′ line showing theeighth embodiment of the light-emitting device shown in FIG. 17A;

FIG. 18 is a cross-sectional diagram showing the ninth embodiment of thelight-emitting device in accordance with the present disclosure;

FIGS. 19A through 19D demonstrate the method for manufacturing thelight-emitting device shown in FIG. 18;

FIG. 20A is a top view of the tenth embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 20B is a cross-sectional diagram along an A-A′ line showing thetenth embodiment of the light-emitting device shown in FIG. 20A;

FIG. 21A is a top view of the eleventh embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 21B is a cross-sectional diagram along an A-A′ line showing theeleventh embodiment of the light-emitting device shown in FIG. 21A;

FIG. 22 is a top view of the twelfth embodiment of the light-emittingdevice in accordance with the present disclosure;

FIG. 23 is a top view of the thirteenth embodiment of the light-emittingdevice in accordance with the present disclosure; and

FIG. 24 is a cross-sectional diagram showing a conventional verticalcavity surface emitting laser (VCSEL).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Exemplary embodiments of the present disclosure will be described indetail with reference to the accompanying drawings hereafter. Thefollowing embodiments are given by way of illustration to help thoseskilled in the art fully understand the spirit of the presentdisclosure. Hence, it should be noted that the present disclosure is notlimited to the embodiments herein and can be realized by various forms.Further, the drawings are not precisely scaled and components may beexaggerated in view of width, height, length, etc. Herein, the similaror identical reference numerals will denote the similar or identicalcomponents throughout the drawings.

In the present disclosure, if not specifically mention, the generalexpression of AlGaAs means Al_(x)Ga_((1−x))As, wherein 0≦x≦1; thegeneral expression of AlInP means Al_(x)In_((1−x))P, wherein 0≦x≦1; thegeneral expression of AlGaInP means (Al_(y)Ga_((1−y)))_(1−x)In_(x)P,wherein 0≦x≦1, 0≦y≦1; the general expression of AlGaN meansAl_(x)Ga_((1−x))N, wherein 0≦x≦1; the general expression of AlAsSb meansAlAs_((1−x))Sb_(x) wherein 0≦x≦1 and the general expression of InGaPmeans In_(x)Ga_(1−x)P, wherein 0≦x≦1. The content of the element can beadjusted for different purposes, such as, but not limited to, adjustingthe energy gap or adjusting the peak wavelength or the dominantwavelength.

FIG. 1A is a top view of the first embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 1B is across-sectional diagram along an A-A′ line showing the first embodimentof the light-emitting device shown in FIG. 1A. In the presentembodiment, the light-emitting device comprises a substrate 10, anepitaxial structure 20 on the substrate 10, a current blocking layer 30,a first electrode 40, and a second electrode 50. The epitaxial structure20 comprises a first DBR stack 21, a light-emitting stack 22 and asecond DBR stack 23 and a contact layer 24 in sequence. The conductivitytype of the first DBR stack 21 is different from that of the second DBRstack 23. In the present embodiment, the first DBR stack 21 is n-type,and the second DBR stack 23 is p-type. The current blocking layer 30 isbetween the contact layer 24 and the first electrode 40. A first opening31 is formed in the current blocking layer 30 to expose the contactlayer 24, and the first opening 31 has a first maximum width w₁. A partof the first electrode 40 fills in the first opening 31 and directlycontacts the contact layer 24. A second opening 25 is formed in thefirst electrode 40 to expose the contact layer 24 and has a secondmaximum width w₂ less than the first maximum width w₁. The secondelectrode 50 is on the side of the substrate 10 opposite to theepitaxial structure 20. The light-emitting device is capable of emittingemit a radiation R having a peak wavelength between 600 nm and 1600 nm,and preferably between 830 nm and 1000 nm.

As shown in FIG. 1B, in the present embodiment, the width of thesubstrate 10, the width of the epitaxial structure 20, and the width ofthe current blocking layer 30 are substantially the same. In the presentembodiment, the first opening 31 has a shape of circle, and the firstmaximum width w₁ is the diameter of the circle. The shape of the firstopening 31 is not limited to the present embodiment. The shape of thefirst opening 31 can be of ellipse, rectangular, square, rhombus or anyother shape. The first maximum width w₁ is, but not limited to, between20 μm and 50 μm. The current blocking layer 30 comprises insulatingmaterial comprising aluminum oxide (Al_(x)O_(y)), silicon oxide(SiO_(x)), silicon oxynitride (SiO_(x)N_(y)), silicon nitride(Si_(x)N_(y)), epoxy, polyimide, perfluorocyclobutane, benzocyclobutene(BCB) or silicone. Preferably, the current blocking layer 30 issubstantially transparent to the radiation emitted by the light-emittingstack 22. The current blocking layer 30 has a thickness greater than 100nm, and preferably less than 2 μm, and more preferably, close or equalto n λ/4, wherein λ is the peak wavelength of the radiation emitted fromthe light-emitting stack 22, and n is an odd positive integer.

In the present embodiment, the second opening 25 has a shape of circle,and the second maximum width w₂ is the diameter of the circle. The shapeof the second opening 25 is not limited to the present embodiment. Theshape of the second opening 25 can be of ellipse, rectangular, square,rhombus or any other shape. Preferably, the shape of the second opening25 is substantially the same as the shape of the first opening 31.Preferably, the first opening 31 and the second opening 25 are with acommon center. More preferably, the first opening 31 and the secondopening 25 are substantially concentric circles.

As shown in FIG. 1A and 1B, the first electrode 40 is a contiguous layerand comprises a bonding portion 41 for bonding a wire, a currentinjection portion 42 for injecting a current through the epitaxialstructure 20, and a bridge portion 43 connecting the bonding portion 41and the current injection portion 42. The bonding portion 41 is on thecurrent blocking layer 30. The current injection portion 42 fills in thefirst opening 31 and contacts the contact layer 24. In one embodiment,the current injection portion 42 is in a form of ring such that thesecond opening 25 is formed within the current injection portion 42.Specifically, in the present embodiment, the current injection portion42 is separated from a side wall of the current blocking layer 30 andthus a gap is formed between the current injection portion 42 and theside wall of the current blocking layer 30, wherein the gap exposes apart of the epitaxial structure 20 as shown in FIG. 1A and FIG. 1B. Thefirst electrode 40 of the present embodiment covers less than 50% of thesurface area of the current blocking layer 30. The current blockinglayer 30 between the bridge portion 43 and the epitaxial structure 20and between the bonding portion 41 and the epitaxial structure 20 is forpreventing a current from directly flowing through the epitaxialstructure 20 from the bonding portion 41 and the bridge portion 43.

In the present embodiment, the light-emitting device is devoid of ahighly resistive structure in the second DBR stack 23, wherein thehighly resistive structure is one layer in the second DBR stack 23directly under the first electrode 40 and thus covered by the firstelectrode 40 and has relatively low conductivity compared toconductivity of the other layers in the second DBR stack 23 directlyunder and thus covered by the first electrode 40. Specifically, thehighly resistive structure is embodied like an oxidized layer, an ionimplanted layer or an undercut aperture as shown in FIG. 24. Morepreferably, the light-emitting device is devoid of an oxidized layer, anion implanted layer and an undercut aperture in the second DBR stack 23directly under the current blocking layer 30 and/or directly under thefirst electrode 40. That is, the conductivity of the portion of thesecond DBR stack 23 directly under the first opening 31 as a whole issubstantially the same as the conductivity of the portion of the secondDBR stack 23 covered by the current blocking layer 30 as a whole.Preferably, the second DBR stack 23 consists essentially of a GroupIII-V semiconductor material, such as AlGaAs. The second DBR stack 23 isdevoid of any oxides, such as aluminum oxide, that are intentionallyformed, wherein aluminum oxide has an empirical formula Al_(a)O_(b),wherein a and b are natural numbers excluding 0. Furthermore, the secondDBR stack 23 is devoid of any conductivity reducing ions that areintentionally formed for reducing the conductivity of a part of thesecond DBR stack 23 more than 3 orders of magnitude, and preferably,more than 5 orders of magnitude, compared to the conductivity of theother part of the second DBR stack 23, which is more conductive. Theconductivity reducing ions comprise Ar ion, He ion, or H ion. The secondDBR stack 23 may comprises inevitable ions existing in the environment,however, since the inevitable ions does not substantially change theconductivity of the second DBR stack 23, for example, the inevitableions does not reduce conductivity more than 1 order of magnitudecompared to the conductivity of the more conductive part of the secondDBR stack 23, the inevitable ions should not be taken into considerationin the present disclosure. In one embodiment, because the light-emittingdevice is devoid of an undercut aperture in the second DBR stack 23 asshown in FIG. 24, each layer of the second DBR stack 23 consistsessentially of a Group III-V semiconductor material and is without airgap in any layer of the second DBR stack 23.

When a current flows into the epitaxial structure 20, because thecurrent injection portion 42 in the first opening 31 directly contactsthe contact layer 24 of the epitaxial structure 20, and because thebonding portion 41 and the bridge portion 43 are separated and insulatedfrom the epitaxial structure 20 by the current blocking layer 30, thecurrent mostly flows through the portion of the epitaxial structure 20not covered by the current blocking layer 30 and directly contacting thecurrent injection portion 42. That is, the current density of theportion of the second DBR stack 23 directly under the current blockinglayer 30 is much lower than the current density of the portion of thesecond DBR stack 23 not covered by the current blocking layer 30 whenthe current flows into the epitaxial structure 20. As a result, theportion of the epitaxial structure 20 directly contacts the currentinjection portion 42 and substantially directly under the first opening31 functions as a radiation emitting region for generating the radiationR. The radiation R escapes out of the light-emitting device through thefirst opening 31. Specifically, the topmost layer of the epitaxialstructure 20, i.e. the contact layer 24 in the present embodiment, isthe first layer in the epitaxial structure 20 to conduct a confinedcurrent in the light-emitting device.

FIG. 2 shows a relationship curve of optical output power vs. forwardcurrent of the first embodiment of the light-emitting device. In thepresent embodiment, the light-emitting device has a forward voltageV_(f), a lasing threshold current I_(th) and a saturation currentI_(sat). The forward voltage V_(f) is at which the light-emitting devicestarts to conduct a significant forward current, for example, in thepresent embodiment, 5 mA. The lasing threshold current I_(th) is theminimum current at which the radiation emitting from the radiationemitting region I of the light-emitting device is dominated bystimulated emission rather than by spontaneous emission, and thereforethe radiation becomes coherent. The saturation current I_(sm) is acurrent at which the radiation output is no longer increased withincreasing forward current. The radiation emitted from the radiationemitting region I of the light-emitting device of the present disclosureis an incoherent light at an operating voltage V_(op) greater than aforward voltage V_(f) of the light-emitting device and at a forwardcurrent less than the lasing threshold current I_(th). Preferably, theincoherent light has a far-field angle of greater than 60 degrees whenthe light-emitting device operates at an operating voltage greater thana forward voltage V_(f) of the light-emitting device and an operatingcurrent less than the lasing threshold current I_(th). The radiation Remitted from the radiation emitting region I of the light-emittingdevice is a coherent light having a far-field angle of less than 15degrees when the light-emitting device operates at a forward currentgreater than the lasing threshold current I_(th) and less than thesaturation current I_(sat). Specifically, when the light-emitting deviceoperates at a forward current substantially equal to the lasingthreshold current I_(th), the part of the epitaxial structure 20 otherthan the radiation emitting region I and other than the part of theepitaxial structure 20 covered by the first electrode 40 emits anincoherent light R₁ since having current density far less than that ofthe radiation emitting region I. The bonding portion 41 and the bridgeportion 43 shields the radiation emitted from the epitaxial structure20.

In the present embodiment, the lasing threshold current I_(th) is about20 mA. The lasing threshold current I_(th), the saturation currentI_(sat) and a difference between the lasing threshold current I_(th) andthe saturation current I_(sat) can be adjusted by the first maximumwidth w₁ of the first opening 31 for different applications. Forexample, if a higher lasing threshold current I_(th), a highersaturation current I_(sat) and a higher difference between the lasingthreshold current I_(th) and the saturation current I_(sat) are needed,the first maximum width w₁ can be larger. Specifically, the lasingthreshold current I_(th) and the first maximum width w₁ fulfill thefollowing equation:

0.4w _(1(μm))−7≦I _(th(mA))≦0.4w _(1(μm))+7

Table 1 shows far-field angles of the radiation of the light-emittingdevice at different forward currents. The far-field angle of the presentdisclosure is determined as the divergent angle at full width at halfmaximum intensity to specify the beam divergence.

TABLE 1 forward current (mA) Far-field angle 20 65.6° 23 5.6° 25 5.8° 306.5° 40 7.9°

From Table 1, when a forward current is higher than the lasing thresholdcurrent I_(th) and lower than the saturation current I_(sat), thefar-field angle of the radiation is less than 15 degrees, andpreferably, between 5 and 15 degrees, and more preferably, between 5 and13 degrees.

In the present disclosure, although the light-emitting device is devoidof a highly resistive structure comprising an oxidized layer and an ionimplanted layer in the second DBR stack 23, by comprising the currentblocking layer 30 and the first electrode 40, which results in thetopmost layer of the epitaxial structure 20 being the first layer of theepitaxial structure 20 to conduct a confined current in thelight-emitting device, the light-emitting device has a far-field anglesmaller than 15 degrees when a forward current is between the lasingthreshold current I_(th) and the saturation current I_(sat). Besides, aconventional light-emitting device comprising a highly resistivestructure, e.g. an oxidized layer, in the second DBR stack 23 has a widefar-field angle under normal operation, especially operating under ahigher forward current. However, the light-emitting device has afar-field angle smaller than 15 degrees when a forward current is in arange between the lasing threshold current I_(th) and the saturationcurrent I_(sat). The light-emitting device is applicable to sensors suchas proximity, night vision systems or oxymeter.

FIG. 3A through FIG. 4B demonstrate the method for manufacturing thelight-emitting device shown in FIG. 1A and FIG. 1B; FIG. 3B is across-sectional diagram along an A-A′ line shown in FIG. 3A; FIG. 4B isa cross-sectional diagram along an A-A′ line shown in FIG. 4A. Themethod comprises the steps of:

-   -   a. referring to FIG. 3A and FIG. 3B, providing a substrate 10;    -   b. forming an epitaxial structure 20 on the substrate 10 by        epitaxial growth;    -   c. forming a current blocking layer 30 on the epitaxial        structure 20 by any suitable method, such as sputtering or        evaporation;    -   d. patterning the current blocking layer 30 by a lithographic        mask to form a first opening 31 to expose a part of the        epitaxial structure 20 by any suitable method;    -   e. forming a metal layer (nor shown) on the current blocking        layer 30 and covering the first opening 31 as shown in FIG. 4A        and FIG. 4B;    -   f. patterning the metal layer by a lithographic mask to form a        first electrode 40, wherein the first electrode 40 comprises a        current injection portion 42, a bonding portion 41 and a bridge        portion 43 connecting the bonding portion 41 and the current        injection portion 42, wherein the bonding portion 41 and the        bridge portion 43 are on the current blocking layer 30, and the        current injection portion 42 fills in the first opening 31, a        second opening 25 is formed in the current injection portion 42        to expose the epitaxial structure 20;    -   g. forming a second electrode 50 on the side of the substrate 10        opposite to the epitaxial structure 20 by any suitable method;        and    -   h. dicing the structure formed at step g to obtain an individual        finished light-emitting device shown in FIG. 1A and FIG. 1B.

The method of the present disclosure is devoid of a step of reducingconductivity in a region in the second DBR stack 23, such as anoxidation step to oxidize at least one layer in the second DBR stack 23,an ion implantation step to implant at least one conductivity reducingion into at least one layer in the second DBR stack 23 and/or an etchingstep to selectively etch away a periphery part of at least one layer inthe second DBR stack 23 to form an undercut aperture such that theconductivity in the oxidized region, the ion implanted region, or theundercut aperture as shown in FIG. 24 is lower than that of the otherregion of the second DBR stack 23.

The oxidation step, the ion implantation step and the step of etchingone of the layers in the second DBR stack 23 are for turning a part ofthe second DBR stack 23 directly under the first electrode 40 into asubstantially insulated region so as to from a highly resistivestructure in the second DBR stack 23. The method of the presentdisclosure uses no more than 4 different lithographic masks forpatterning process. In the present embodiment, the method uses only twodifferent lithographic masks for patterning process. As a result, themethod for manufacturing the light-emitting device is simple and costeffective.

FIG. 5A is a top view of the second embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 5B is across-sectional diagram along an A-A′ line of the light-emitting deviceshown in FIG. 5A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the second embodiment of thepresent disclosure comprises substantially the same structure as thefirst embodiment, and the difference is that the width of the currentblocking layer 30 is less than the width of the epitaxial structure 20.As a result, a periphery part of the epitaxial structure 20 is exposedfrom the current blocking layer 30 from a top view of the light-emittingdevice. Besides, the first electrode 40 has a shape different from thatof the first embodiment. Specifically, the first electrode 40 covers thewhole side wall of the current blocking layer 30 enclosing the firstopening 31 and thus only exposes the contact layer 24 directly under thesecond opening 25. As a result, the epitaxial structure 20 directlycontacts the current injection portion 42 and substantially directlyunder the first opening 31 functions as a radiation emitting region I,and the radiation R escapes out of the surface of the light-emittingdevice mainly through the second opening 25. Furthermore, the firstelectrode 40 covers more than 50% of the surface area of the currentblocking layer 30, and the first electrode 40 has a shape substantiallythe same as the shape of the current blocking layer 30. Preferably, thefirst electrode 40 covers more than 80% of the surface area of thecurrent blocking layer 30, and more preferably, more than 90% of thesurface area of the current blocking layer 30. A part of the firstelectrode 40 away from the second opening 25 is for bonding a wire.Because the first electrode 40 covers a large surface area of thecurrent blocking layer 30 and covers the whole side wall of the currentblocking layer 30 enclosing the first opening 31, when a forward currentis higher than the lasing threshold current I_(th) of the light-emittingdevice, an incoherent light emitted from the light-emitting stack 22directly under most part of the first electrode 40 is shielded by thefirst electrode 40 while a coherent light emitted from thelight-emitting stack 22 escapes from the second opening 25. The methodfor manufacturing the light-emitting device as shown in FIG. 5A and FIG.5B is substantially the same as the method for manufacturing thelight-emitting device as shown in FIG. 1A and FIG. 1B except that thelithographic mask for patterning the metal layer is different andtherefore, the pattern of the first electrode 40 in the secondembodiment is different from the pattern of the first electrode 40 inthe first embodiment.

FIG. 6 is a cross-sectional diagram showing the third embodiment of thelight-emitting device in accordance with the present disclosure. Thesame reference number given or appeared in different paragraphs orfigures along the specification should has the same or equivalentstructure, material, material composition, the manufacturing processthereof while it is once defined anywhere of the disclosure except it isspecifically described differently. The light-emitting device inaccordance with the third embodiment of the present disclosure comprisessubstantially the same structure as the second embodiment, and thedifference is that a periphery part of the epitaxial structure 20 isremoved by any suitable method so as to form a ridge 26 having a widthsmaller than the width of the substrate 10 and comprising an exposedmesa wall 261 closer to the second opening 25 compared to the outermostedge of the substrate 10. Specifically, the current blocking layer 30covers along the mesa wall 261 and a top surface of the first DBR stack21. In the present embodiment, the mesa wall 261 of the ridge 26 of theepitaxial structure 20 is protected by the current blocking layer 30. Asa result, the reliability of the epitaxial structure 20 and thereliability of the light-emitting device are improved. The method formanufacturing the light-emitting device as shown in FIG. 6 issubstantially the same as the method for manufacturing thelight-emitting device as shown in FIG. 5A and FIG. 5B. The difference isthat before forming a current blocking layer 30 on the epitaxialstructure 20, the method further comprises steps of patterning theepitaxial structure 20 by removing a periphery part of the second DBRstack 23, a periphery part of light-emitting stack 22, and a portion ofa periphery part of the first DBR stack 21 of the epitaxial structure 20by any suitable method to form a ridge 26 comprising a mesa wall 261. Inthe present embodiment, the method of the present disclosure uses nomore than 3 different lithographic masks for patterning process. As aresult, the method for manufacturing the light-emitting device is simpleand cost effective.

FIG. 7 is a cross-sectional diagram showing the fourth embodiment of thelight-emitting device. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the fourth embodiment of thepresent disclosure comprises substantially the same structure as thethird embodiment, and the difference is that the first electrode 40covers on the current blocking layer 30 along the mesa wall 261 and thusthe current blocking layer 30 is between the epitaxial structure 20 andthe first electrode 40. The first electrode 40 covering on the currentblocking layer 30 along the mesa wall 261 prevents radiation emittedfrom the light-emitting stack 22 from emitting from the mesa wall 261.The method for manufacturing the light-emitting device as shown in FIG.7 is substantially the same as the method for manufacturing thelight-emitting device as shown in FIG. 6 except that the lithographicmask for patterning the metal layer is different.

FIG. 8A is a top view of the fifth embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 8B is across-sectional diagram along an A-A′ line of the light-emitting deviceshown in FIG. 8A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the fifth embodiment of thepresent disclosure comprises substantially the same structure as thefourth embodiment, and the difference is that the first opening 31 is ina form of an annular ring defined by the current blocking layer 30. Thecurrent blocking layer 30 comprises an inner part 301, an outer part302, and the first maximum width w₁ is the diameter of the circleenclosed by the outer part 302. The first opening 31 separates the innerpart 301 of the current blocking layer 30 from the outer part 302 of thecurrent blocking layer 30 for protecting the radiation emitting regionI. The current blocking layer 30 in the present embodiment has athickness substantially equals to n λ/4, wherein λ is the peakwavelength of the radiation emitted from the light-emitting stack 22,and n is an odd positive integer. The first electrode 40 fills in thefirst opening 31, covers along the side wall of the inner part 301 ofthe current blocking layer 30 and is on the periphery part of the innerpart 301 of the current blocking layer 30. The second opening 25 exposesthe underlying inner part 301 of the current blocking layer 30. Themethod for manufacturing the light-emitting device as shown in FIG. 8Aand FIG. 8B is substantially the same as the method for manufacturingthe light-emitting device as shown in FIG. 7 except that thelithographic mask for patterning the current blocking layer 30 isdifferent.

FIG. 9A is a top view of the sixth embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 9B is across-sectional diagram along an A-A′ line of the light-emitting deviceshown in FIG. 9A. FIG. 10A shows a top view of the current blockinglayer 30 of the sixth embodiment of the light-emitting device; FIG. 10Bshows a cross-sectional diagram along an A-A′ line of the light-emittingdevice shown in FIG. 10A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the sixth embodiment of thepresent disclosure comprises substantially the same structure as thefourth embodiment, and the difference is that the light-emitting devicein the present embodiment comprises multiple radiation emitting regionsI arranged in a two-dimensional array in a single chip. Specifically,multiple first openings 31 are formed in the current blocking layer 30to expose the contact layer 24. The current blocking layer 30 is acontiguous layer as shown in FIG. 10A. The first openings 31 areseparated from one another by the current blocking layer 30. Multiplesecond openings 25 arranged in a two-dimensional array are formed in thefirst electrode 40 and are separated from one another, wherein each ofthe second openings 25 is correspondingly formed within one of the firstopenings 31 to expose the contact layer 24 such that the correspondingfirst opening 31 and second opening 25 are concentric. The firstelectrode 40 is a contiguous layer and has a bonding portion 41 withouthaving any second openings 25 formed therein for bonding a wire. A partof the first electrode 40 fills in the first openings 31, covers alongthe side walls of the current blocking layer 30 enclosing the firstopenings 31 and direct contacts the contact layer 24 of the epitaxialstructure 20. The region of the epitaxial structure 20 directlycontacting the first electrode 40 and substantially directly under thefirst openings 31 functions as radiation emitting regions I. Thearrangement of the radiation emitting regions I is not limited to thepresent embodiment, for example, the radiation emitting regions I can bearranged in a staggered arrangement or the numbers of the radiationemitting regions I of two adjacent rows and/or columns can be different.

FIG. 11A is a top view of the seventh embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 11B is across-sectional diagram along an A-A′ line of the light-emitting deviceshown in FIG. 11A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. In thepresent embodiment, the substrate 10, the first DBR stack 21, thelight-emitting stack 22, the second DBR stack 23 are substantially thesame as the second embodiment. The difference is that the contact layer24 has a first width w₃, and the second DBR stack 23 has a second widthw₄ greater than the first width w₃. The light-emitting device furthercomprises a conductive layer 60 covering the contact layer 24 andinterposed between the first electrode 40 and the contact layer 24. Theconductive layer 60 has a third width w₅ substantially the same as thesecond width w₄ of the second DBR stack 23. The first electrode 40covers more than 50% of the surface area of the conductive layer 60.Preferably, the first electrode 40 covers more than 80%, and morepreferably, more than 90% of the surface area of the conductive layer60. The first electrode 40 has a contour substantially the same as thecontour of the conductive layer 60. The first electrode 40 directlycontacts the conductive layer 60 instead of directly contacting thecontact layer 24. The second DBR stack 23, the light-emitting stack 22and the first DBR stack 21 directly under the contact layer 24 functionsas a radiation emitting region I. The radiation R escapes out of thelight-emitting device through the second opening 25.

The second opening 25 is directly over the contact layer 24 and exposesthe underlying conductive layer 60. A ratio of the first width w₃ of thecontact layer 24 to the second maximum width w₂ of the second opening 25is between 0.1 and 3, and preferably, is between 0.5 and 1.1, and morepreferably between 0.6 and 0.8. By having the ratio of the first widthw₃ to the second maximum width w₂ less than 1, the first electrode 40 isless likely to shield the light generating from the radiation emittingregion I, and thus more light escapes from the second opening 25.

The conductivity of the portion of the second DBR stack 23 directlyunder the contact layer 24 is substantially the same as the conductivityof the portion of the second DBR stack 23 not covering by the contactlayer 24. The conductive layer 60 has an thickness substantially equalto n λ/4, wherein λ is the peak wavelength of the radiation emitted fromthe light-emitting stack 22, and n is an odd positive integer. Theconductive layer 60 comprises transparent conductive metal oxidematerial, such as indium tin oxide (ITO), aluminum zinc oxide (AZO),SnCdO, antimony tin oxide (ATO), ZnO, Zn₂SnO₄ (ZTO) or indium zinc oxide(IZO). The conductive layer 60 is substantially transparent to theradiation emitted by the light-emitting stack 22.

When a current flows into the epitaxial structure 20 from the firstelectrode 40, because the contact resistance between the contact layer24 and the second DBR stack 23 is relatively lower than the contactresistance between the conductive layer 60 and the epitaxial structure20, the current mostly flows from the conductive layer 60 toward thecontact layer 24, and then into the epitaxial structure 20 mainlythrough the contact layer 24. That is, the current density of theportion of the second DBR stack 23 directly under the contact layer 24is much higher than the current density of the portion of the second DBRstack 23 without being covered by the contact layer 24. Specifically,the topmost layer of the epitaxial structure 20, in the presentembodiment, the contact layer 24, is the first layer in the epitaxialstructure 20 to conduct a confined current in the light-emitting device.

FIG. 12A is a radiation output vs. forward current curve of thelight-emitting device of the seventh embodiment, wherein the ratio ofthe first width w₃ of the contact layer 24 to the second maximum widthw2 of the second opening 25 is about 1. FIG. 12B is a graph showing anenlarged detail of region I in FIG. 12A. In the present embodiment, thelasing threshold current I_(th) is about 13 mA, and the saturationcurrent I_(sat) is about 79 mA. The lasing threshold current I_(th), thesaturation current I_(sat) and a difference between the lasing thresholdcurrent I_(th) and the saturation current I_(sat) can be adjusted by thefirst width w₃ of the contact layer 24 for different applications, forexample, if a higher lasing threshold current I_(th), a highersaturation current I_(sat) and a higher difference between the lasingthreshold current I_(th) and the saturation current I_(sat) are needed,the first width w₃ can be larger. Specifically, the lasing thresholdcurrent I_(th) and the first width w₃ fulfill the following equation:

0.4w _(3(μm))−7≦I _(th(mA))≦0.4w _(3(μm))+7

In one embodiment, the radiation having a peak wavelength about 850±10nm. In one embodiment, the radiation having a peak wavelength about940±10 nm.

Table 2 shows far-field angles of the radiation having a peak wavelengthof 850±10 nm emitted by the light-emitting device of the seventhembodiment at different forward currents.

TABLE 2 forward current (mA) Far-field angle 15 10.54° 18 10.90° 2210.9°

Table 3 shows far-field angles and radiation output of the radiationhaving a peak wavelength of 940±10 nm of the light-emitting device ofthe seventh embodiment at different forward currents. In the presentembodiment, the lasing threshold current I_(th) is about 13 mA, and thesaturation current is about 80 mA.

TABLE 3 injected current (mA) Far-field angle P₀(mW) 15 9.61° 1.09 1811.03° 1.95 22 11.19° 3.2

From Table 2 and 3, when a forward current is higher than the lasingthreshold current I_(th) and lower than the saturation current I_(sat),the far-field angle of the radiation is less than 15 degrees, andpreferably, between 5 and 15 degrees, and more preferably, between 8 and13 degrees.

In the present disclosure, although the light-emitting device is devoidof a highly resistive structure comprising an oxidized layer and an ionimplanted layer in the second DBR stack 23, by comprising the contactlayer 24 and the conductive layer 60, which results in the topmost layerof the epitaxial structure 20 being the first layer in the epitaxialstructure 20 to conduct a confined current in the light-emitting device,the light-emitting device has a far-field angle smaller than 15 degreeswhen a forward current is in a range between the lasing thresholdcurrent I_(th) and the saturation current I_(sat).

FIGS. 13A through 16B demonstrate the method for manufacturing thelight-emitting device shown in FIG. 11A and FIG. 11B. The methodcomprises the steps of:

-   -   a. referring to FIG. 13A and FIG. 13B, providing a substrate 10;    -   b. forming an epitaxial structure 20 on the substrate 10 by        epitaxial growth;    -   c. patterning the contact layer 24 by a lithographic mask;    -   d. referring to FIG. 14A and FIG. 14B, forming a conductive        layer 60 covering the patterned contact layer 24 by any suitable        method such as sputtering or evaporation;    -   e. referring to FIG. 15A and FIG. 15B, forming a metal layer        (nor shown) on the conductive layer 60;    -   f. patterning the metal layer by a lithographic mask to form a        first electrode 40 and a second opening 25 in the first        electrode 40, wherein the first electrode 40 has a pattern        substantially complementary to t the pattern of the contact        layer 24, that is, the pattern of the contact layer 24 is        substantially the same as that of the second opening 25 of the        first electrode 40; the second opening 25 is substantially        directly over the contact layer 24;    -   g. referring to FIG. 16A and FIG. 16B, removing a periphery part        of the epitaxial structure 20 to form a ridge 26 comprising an        exposed mesa wall 261 closer to the second opening 25 compared        to the outermost edge of the substrate 10;    -   h. forming a second electrode 50 on the side of the substrate 10        opposite to the epitaxial structure 20; and i. dicing the        structure formed at step h to obtain an individual finished        light-emitting device as shown in FIG. 11A and FIG. 11B.

The method of the present disclosure is also devoid a step of reducingconductivity of one layer in the second DBR stack 23, such as anoxidation step, an ion implantation step to implant at least oneconductivity reducing ion into at least one layer in the second DBRstack 23 and/or an etching step to selectively etch away a peripherypart of at least one layer in the second DBR stack 23 to form anundercut aperture such that the conductivity in the oxidized region, theion implanted region, or the undercut aperture as shown in FIG. 24 islower than the other region of the second DBR stack 23. The oxidationstep, the ion implantation step and the step of etching one of thelayers in the second DBR stack 23 are for turning a part of the secondDBR stack 23 directly under the first electrode 40 into a substantiallyinsulated region so as to from a highly resistive structure in thesecond DBR stack 23. Preferably, the method of the present disclosureuses no more than 3 different lithographic masks for patterning process.As a result, the method for manufacturing the light-emitting device issimple and cost effective.

FIG. 17A is a top view of the eighth embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 17B is across-sectional diagram along line A-A′ of the light-emitting deviceshown in FIG. 17A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the eighth embodiment of thepresent disclosure comprises substantially the same structure as theseventh embodiment, and the difference is that the light-emitting devicefurther comprises a passivation layer 110 substantially and conformablycovering the epitaxial structure 20, the conductive layer 60 and thefirst electrode 40. The passivation layer 110 comprises an opening 111exposing the underlying first electrode 40 and away from the contactlayer 24 for a wire bonded thereto. The method for manufacturing thelight-emitting device as shown in FIG. 17A and FIG. 17B is substantiallythe same as the method for manufacturing the light-emitting device asshown in FIG. 16A and FIG. 16B. The difference is that after the step offorming a ridge 26 comprising an exposed mesa wall 261, the methodfurther comprises steps of conformably forming a passivation layer 110along the exposed mesa wall 261 of the epitaxial structure 20, along aside wall of the conductive layer 60, along a side wall of the firstelectrode 40 and covering the conductive layer 60 and the firstelectrode 40; then, patterning the passivation layer 110 to form anopening 111 in the passivation layer 110 for exposing the underlyingfirst electrode 40. The method of the present disclosure uses no morethan 4 different lithographic masks for patterning process. As a result,the method for manufacturing the light-emitting device is simple andcost effective.

FIG. 18 is a cross-sectional diagram showing the ninth embodiment of thelight-emitting device. The top view of the light-emitting device issubstantially the same as shown in FIG. 11A. The same reference numbergiven or appeared in different paragraphs or figures along thespecification should has the same or equivalent structure, material,material composition, the manufacturing process thereof while it is oncedefined anywhere of the disclosure except it is specifically describeddifferently. The light-emitting device in accordance with the eighthembodiment of the present disclosure comprises substantially the samestructure as the seventh embodiment, and the difference is that thelight-emitting device of the present embodiment comprises a permanentsubstrate 90 and a bonding layer 100 between the permanent substrate 90and the epitaxial structure 20. In the present embodiment, the permanentsubstrate 90 has a thermal conductivity higher than that of thesubstrate 10. The bonding layer 100 is for connecting the permanentsubstrate 90 and the epitaxial structure 20. FIGS. 19A through 19Ddemonstrate the method for manufacturing the light-emitting device shownin FIG. 18. The method for manufacturing the light-emitting device asshown in FIG. 18 is substantially the same as the method formanufacturing the light-emitting device as shown in FIG. 11A and FIG.11B. The difference is that before patterning the contact layer 24, themethod further comprises the steps of bonding the epitaxial structure 20to a temporary substrate 70 by a temporary bonding layer 80 as shown inFIG. 19A, in the present embodiment, wherein the temporary substrate 70comprises glass; removing the substrate 10 by any suitable method asshown in FIG. 19B; bonding the epitaxial structure 20 to a permanentsubstrate 90 by a bonding layer 100 as shown in FIG. 19C; and removingthe temporary substrate 70 and the temporary bonding payer 80 as shownin FIG. 19D. In the present embodiment, by the method comprising thebonding steps, the light-emitting device comprises the permanentsubstrate 90 with a higher thermal conductivity. As a result, thelight-emitting device achieves a higher output power.

FIG. 20A is a top view of the tenth embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 20B is across-sectional diagram along an A-A′ line showing the light-emittingdevice shown in FIG. 20A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the tenth embodiment of thepresent disclosure comprises substantially the same structure as theseventh embodiment, and the difference is that the light-emitting devicein the present embodiment comprises multiple radiation emitting regionsI arranged as an array in a single chip. Specifically, the contact layer24 comprises multiple discrete contact regions 241 arranged in atwo-dimensional array as shown in FIG. 20A. Each contact region 241 hasa first width w₃. In the present embodiment, the first widths w₃ of thecontact regions 241 are substantially the same. The conductive layer 60is a contiguous layer and covering the multiple discrete contact regions241 as shown in FIG. 20B. The first electrode 40 is on the conductivelayer 60 and is a contiguous layer. Multiple second openings 25 areformed in the first electrode 40 and are separated from one another,wherein each of the second openings 25 is correspondingly formed toalign with one of the contact regions 241. The second openings 25 exposethe conductive layer 60. A ratio of the width of one of the contactregions 241 to the second width w₂ of the second opening 25 is between0.1 and 3, and preferably, is between 0.9 and 1.1. In the presentembodiment, the ratios are substantially the same. The second DBR stack23, the light-emitting stack 22 and the first DBR stack 21 that aredirectly under the contact regions 241 and exposed by the secondopenings 25 function as radiation emitting regions I. The number of thecontact regions 241 and the second openings 25 are not limited to thepresent embodiment, and the arrangement of the radiation emittingregions I is not limited to the present embodiment, for example, theradiation emitting regions I can be arranged in a staggered arrangementor the numbers of the radiation emitting regions I of two adjacent rowsand/or columns can be different. Specifically, the topmost layer of theepitaxial structure 20, in the present embodiment, the contact layer 24,is the first layer in the epitaxial structure 20 to conduct a confinedcurrent in the light-emitting device.

FIG. 21A is a top view of the eleventh embodiment of the light-emittingdevice in accordance with the present disclosure; FIG. 21B is across-sectional diagram along an A-A′ line showing the light-emittingdevice shown in FIG. 21A. The same reference number given or appeared indifferent paragraphs or figures along the specification should has thesame or equivalent structure, material, material composition, themanufacturing process thereof while it is once defined anywhere of thedisclosure except it is specifically described differently. Thelight-emitting device in accordance with the eleventh embodiment of thepresent disclosure comprises substantially the same structure as thetenth embodiment, and the difference is that the width w_(3′) of atleast one of the contact regions 241 is different from the width w₃ ofother contact regions so as to have multiple different lasing thresholdcurrents I_(th). In the present embodiment, the widths w_(3′) of thecontact regions 241 in the middle column are smaller than the widths w₃of the other contact regions 241 as shown in FIG. 21B. The differencebetween the width of one of the contact regions 241 in the middle columnand the width of one of the other contact regions 241 in other twocolumns is not less than 3 μm, and preferably, larger than 8 μm, andpreferably less than 40 μm. The second openings 25 aligning with thecontact regions 241 in the middle column is smaller than the othersecond openings 25 as shown in FIG. 21A. The ratio of the width of thecontact regions 241 to the second maximum width w₂ of the correspondingsecond opening 25 is between 0.1 and 3, and preferably, is between 0.5and 1.1, and more preferably between 0.6 and 0.8. The light-emittingdevice comprises multiple different lasing threshold currents I_(th).Each of the lasing threshold currents I_(th) is for generating acoherent light from one of the radiation emitting regions I.Specifically, because the widths w_(3′) of the contact regions 241 aresmaller than the widths w₃ of the other contact regions 241, the lasingthreshold current I_(th) for a emitting coherent light from one of theradiation emitting regions I in the middle column are smaller than thelasing threshold current I_(th) for emitting a coherent light from oneof the radiation emitting regions I in the other two columns. As aresult, in the present embodiment, with an forward current greater thanthe lasing threshold current I_(th) for emitting a coherent light fromone of the radiation emitting regions I in the middle column and lessthan the lasing threshold current I_(th) for emitting a coherent lightfrom one of the radiation emitting regions I in the other two columns,the radiations emitted from the radiation emitting regions I in themiddle column are coherent light each having a far-field angle of lessthan 15 degrees while the radiations emitted from the other radiationemitting regions I are incoherent lights each having a far-field angleof greater than 60 degrees. Therefore, the light-emitting device issuitable for applications required both long-distance and short-distanceproperties such as security cameras. The arrangement of the contactregions 241 having different widths are not limited to the presentembodiment. For example, the contact regions 241 having a width smallerthat of the others can be arranged in the first column. Or, the contactregion with a smaller width and the contact region with a larger widthcan be arranged alternately in a row and/or in a column so as to bearranged in a staggered arrangement.

FIG. 22 is a top view of the twelfth embodiment of the light-emittingdevice in accordance with the present disclosure. The same referencenumber given or appeared in different paragraphs or figures along thespecification should has the same or equivalent structure, material,material composition, the manufacturing process thereof while it is oncedefined anywhere of the disclosure except it is specifically describeddifferently. The light-emitting device in accordance with the twelfthembodiment of the present disclosure comprises substantially the samestructure as the eleventh embodiment, and the difference is that thelight-emitting device comprises multiple lasing threshold currentsI_(th) substantially the same with one another. Each of the lasingthreshold currents I_(th) is for generating a coherent light from one ofthe radiation emitting regions I. By using a different layout of thefirst electrode 40 to control different amounts of current injectinginto different contact regions 241, one of the contact regions 241 drawsmore current compared to the current drawn to the other contact regions241 when a current flows into the light-emitting device. Specifically,in the present embodiment, each width of the contact regions 241 in themiddle column is substantially the same as each width of the othercontact regions 241.

Each second opening 25 aligning with the contact region 241 in themiddle column has a width substantially the same as each width of theother second openings 25. The first electrode 40 on the conductive layer60 has a different layout compared to the first electrode 40 as shown inFIG. 21A. Specifically, the first electrode 40 has a bonding portion 41and multiple first extensions 44 and second extensions 45. The bondingportion 41 is for a wire to be bonded thereto. The first extension 44each surrounds one of the second openings 25. Each of the secondextensions 45 substantially perpendicularly extends from the bondingportion 41 and connects to at least three of the first extensions 44. Inthe present embodiment, each width of the first extension 44 issubstantially the same as one another. Each width of the secondextension 45 is substantially the same as one another. The firstextensions 44 surrounding the second openings 25 in the middle columnconnect to two second extensions 45 while the first extensions 44surrounding the second openings 25 in the other two columns connect toonly one second extension 45. As a result, when driving thelight-emitting device, each of the contact regions 241 in the middlecolumn draws more current compared to the current drawn to the othercontact regions 241. When the forward current passing through eachcontact region in the middle column reaches the lasing threshold currentI_(th) of the corresponding radiation emitting regions I, the forwardcurrent passing through each contact region in the other two columns isstill less than the lasing threshold current I_(th) of the correspondingradiation emitting regions I. As a result, the radiations emitted fromthe radiation emitting regions I in the middle column are coherentlights each having a far-field angle of less than 15 degrees while theradiations emitted from the other radiation emitting regions I columnare incoherent lights each having a far-field angle of greater than 60degrees. Therefore, the light-emitting device is suitable forapplications requiring both long-distance and short-distance propertiessuch as security cameras. In another embodiment, to obtain the sameresult, the width of one of the first extensions 44 in the middle columnmay be greater than the width of one of the first extensions 44 in theother two columns. In another embodiment, to obtain the same result, thewidth of the second extension 45 in the middle column may be greaterthan the width of one of the second extension 45 in the other twocolumns instead of comprising two second extensions 45 connected to thefirst extensions 44 in the middle column. The arrangement of the firstextensions 44 and the second extensions 45 is not limited to the presentembodiment. For example, the first extensions 44 surrounding the secondopenings 25 in the first column may also connect to two secondextensions 45, and the width of the first extensions 44 and the width ofthe second extensions 45 can be changed correspondingly.

FIG. 23 is a top view of the thirteenth embodiment of the light-emittingdevice in accordance with the present disclosure. The same referencenumber given or appeared in different paragraphs or figures along thespecification should has the same or equivalent structure, material,material composition, the manufacturing process thereof while it is oncedefined anywhere of the disclosure except it is specifically describeddifferently. The light-emitting device in accordance with the thirteenthembodiment of the present disclosure comprises substantially the samestructure as the twelfth embodiment, and the difference is that thefirst electrode 40 has a different layout on the conductive layer 60.The first electrode 40 comprising a third extension 46 having a widthwider than the width of the first extension 44 and the width of thesecond extension 45. As a result, the third extension 46 covers a largerarea of the periphery part of the second openings 25 in the middlecolumn compared to an area of the periphery part of the second openings25 covered by the first extensions 44 and the second extensions 45 inthe other two columns. As a result, the contact area between theconductive layer 60 and the first electrode 40 surrounding the secondopenings 25 in the middle column are greater than the contact areabetween the conductive layer 60 and the first electrode 40 surroundingthe other second openings 25. Therefore, when driving the light-emittingdevice, each of the contact regions 241 in the middle column draws morecurrent compared to the current drawn to the other contact regions 241.When the forward current passing through each contact region 241 in themiddle column reaches the lasing threshold current I_(th) of thecorresponding radiation emitting regions I, the forward current passingthrough each contact region in the other two columns is still less thanthe lasing threshold current I_(th) of the corresponding radiationemitting regions I. As a result, the radiations emitted from theradiation emitting regions I in the middle column are coherent lightseach having a far-field angle of less than 15 degrees while theradiations emitted from the other radiation emitting regions I columnare incoherent lights each having a far-field angle of greater than 60degrees. Therefore, the light-emitting device is suitable forapplications requiring both long-distance and short-distance propertiessuch as security cameras. The layout of the first extensions 44 and thesecond extensions 45 is not limited to the present embodiment. Forexample, the first electrode 40 may cover a larger area of the peripherypart of the second openings 25 in the first column instead of in themiddle column.

The light-emitting stack 22 comprises an active region comprises asingle heterostructure (SH), a double heterostructure (DH), or amulti-quantum well (MQW) structure. Preferably, the active regioncomprises a multi-quantum well (MQW) structure comprising alternate welllayers and barrier layers. The band gap of each barrier layer is higherthan the band gap of one of the well layers. The peak wavelength of thelight emitted from the active region can be changed by adjusting thethicknesses and the material of the well layers. Preferably, thematerial of the well layers comprises a Group III-V semiconductormaterial, such as AlGaAs. The material of the barrier layers comprises aGroup III-V semiconductor material, such as AlGaAs. The light-emittingstack 22 may further comprise a space layer between the active regionand the first DBR stack 21 and/or between the active region and thesecond DBR stack 23 for adjusting the total thickness of thelight-emitting stack 22 to substantially satisfy a thickness equal to nλ/2, wherein λ is the peak wavelength of the radiation emitted from thelight-emitting stack 22, and n is an positive integer. The material ofthe space layer comprises a Group III-V semiconductor material, such asAlGaAs.

The first DBR stack 21 and second DBR stack 23 comprise a plurality ofalternating semiconductor layers of high and low indices of refraction.The material of the first DBR stack 21 and second DBR stack 23 comprisea Group III-V semiconductor material, such asAl_(x)Ga_((1−x))As/Al_(y)Ga_((q−y))As, wherein x is different from y,and the content of Al and Ga can be adjusted for reflecting apredetermined wavelength range. Each semiconductor layer has a thicknesssubstantially equal to λ/4n, wherein λ is peak wavelength of theradiation emitted from the light-emitting stack 22, and n is therefractive index of the layer. The first DBR stack 21 has a reflectivityof over 99% at the peak wavelength. The second DBR stack 23 has areflectivity of over 98% at the peak wavelength. Preferably, thereflectivity of the first DBR stack 21 is higher than that of the secondDBR stack 23. The pair number of the first DBR stack 21 is greater thanthe pair number of the second DBR stack 23, wherein a semiconductorlayer of high refractive index and a semiconductor layer of lowrefractive index are considered as a pair. Preferably, the pair numberof the first DBR stack 21 is greater than 15, and more preferably,greater than 30, and less than 80. The pair number of the second DBRstack 23 is greater than 15, and more preferably, greater than 20, andless than 80.

In the present embodiment, the substrate 10 provides a top surface forepitaxially growing the epitaxial structure 20. The substrate 10 has athickness thick enough for supporting the layers or the structures grownthereon. Preferably, the substrate 10 has a thickness not less than 100μm, and preferably, not greater than 250 μm. The substrate 10 is singlecrystal and comprises a semiconductor material, for example, a GroupIII-V semiconductor material or a Group IV semiconductor material. Inone embodiment, the substrate 10 comprises a Group III-V semiconductormaterial of n-type or p-type. In the present embodiment, the Group III-Vsemiconductor material comprises GaAs of n-type. The n-type dopantcomprises Si.

The permanent substrate 80 is electrically conductive for conducting acurrent flowing between the first electrode 40 and the second electrode50. The permanent substrate 80 has a thickness thick enough forsupporting the layers or structures thereon, for example, greater than100 μm. The substrate comprises a conductive material comprising Si, Ge,Cu, Mo, MoW, AlN, ZnO or CuW. Preferably, the permanent substrate 80comprises Si or CuW.

The first electrode 40 and the second electrode 50 are for electricallyconnected to an external power source and for conducting a currenttherebetween. The material of the first electrode 40 and the secondelectrode 50 comprise transparent conductive material or metal material,wherein the transparent conductive material comprises transparentconductive oxide, and wherein the metal material comprises Au, Pt,GeAuNi, Ti, BeAu, GeAu, Al, or ZnAu, Ni.

The first electrode 40 forms a low resistance contact or an ohmiccontact with the second DBR stack 23 through the contact layer 24wherein the resistance between first electrode 40 and the second DBRstack 23 is lower than 10⁻² ohm-cm. The conductivity type of the contactlayer 24 is the same as that of the second DBR stack 23. In oneembodiment, the contact layer 24 is p-type and has a high p-typeimpurity concentration, such as greater than 10¹⁸/cm³, and preferably,greater than 10¹⁹/cm³, and more preferably, between 1×10¹⁹/cm³ and5×10²²/cm³ both inclusive.

The material of the contact layer comprises a Group III-V semiconductormaterial, such as GaAs, AlGaAs.

The bonding layer 100 and/or the temporary bonding payer 80 comprisestransparent conducive oxide, metal material, insulating oxide, orpolymer. The transparent conducive oxide comprises indium tin oxide(ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO),antimony tin oxide (ATO), aluminium zinc oxide (AZO), zinc tin oxide(ZTO), gallium doped zinc oxide(GZO), tungsten doped indium oxide (IWO),zinc oxide (ZnO), or indium zinc oxide (IZO). The metal materialcomprises In, Sn, Au, Ti, Ni, Pt, W or the alloys thereof. Theinsulating oxide comprises aluminum oxide (AlO_(x)), silicon oxide(SiO_(x)), or silicon oxynitride (SiO_(x)N_(y)). The polymer comprisesepoxy, polyimide, perfluorocyclobutane, benzocyclobutene (BCB) orsilicone. The bonding layer has a thickness between 400 nm and 5000 nm.

The method of performing epitaxial growth comprises, but is not limitedto metal-organic chemical vapor deposition (MOCVD), hydride vapor phaseepitaxy (HVPE), molecular beam epitaxy (MBE), or liquid-phase epitaxy(LPE).

In accordance with a further embodiment of the present disclosure, thestructures in the embodiments of the present disclosure can be combinedor changed. For example, the light-emitting device as shown in FIGS. 1Aand 1B comprises the passivation layer.

The foregoing description of preferred and other embodiments in thepresent disclosure is not intended to limit or restrict the scope orapplicability of the inventive concepts conceived by the Applicant. Inexchange for disclosing the inventive concepts contained herein, theApplicant desires all patent rights afforded by the appended claims.Therefore, it is intended that the appended claims include allmodifications and alterations to the full extent that they come withinthe scope of the following claims or the equivalents thereof.

What is claimed is:
 1. A light-emitting device comprising: an epitaxialstructure comprising a first DBR stack, a light-emitting stack and asecond DBR stack and a contact layer in sequence; an electrode on theepitaxial structure; a current blocking layer between the contact layerand the electrode; a first opening formed in the current blocking layer;and a second opening formed in the electrode and within the firstopening; wherein a part of the electrode fills in the first opening andcontacts the contact layer.
 2. The light-emitting device according toclaim 1, further comprising a substrate under the epitaxial structure,wherein the substrate has a first width, the epitaxial structurecomprises a ridge having a width smaller than the first width of thesubstrate and comprises an exposed mesa wall, and the current blockinglayer covers the exposed mesa wall.
 3. The light-emitting deviceaccording to claim 2, wherein the electrode covers the exposed mesawall, and wherein the current blocking layer is between the exposed mesawall and the electrode.
 4. The light-emitting device according to claim1, wherein each layer of the second DBR stack consists essentially of aGroup III-V semiconductor material
 5. The light-emitting deviceaccording to claim 1, wherein the conductivity of a portion of thesecond DBR stack right under the first opening is substantially the sameas the conductivity of the other portion of the second DBR stack coveredby the current blocking layer.
 6. The light-emitting device according toclaim 1, wherein the first opening has a first maximum width, and thesecond opening exposes the contact layer and has a second maximum widthless than the first maximum width.
 7. The light-emitting deviceaccording to claim 1, wherein the current blocking layer comprises aninner part and an outer part separated from the inner part.
 8. Thelight-emitting device according to claim 7, wherein the electrode coversalong a side wall of the inner part of the current blocking layer in thefirst opening and is on a periphery part of the inner part of thecurrent blocking layer.
 9. The light-emitting device according to claim8, wherein the second opening exposes a part of the inner part of thecurrent blocking layer.
 10. The light-emitting device according to claim1, further comprising a growth substrate on which the epitaxialstructure is epitaxially grown.
 11. The light-emitting device accordingto claim 1, wherein the light-emitting device is devoid of an oxidizedlayer and an ion implanted layer in the second DBR stack.
 12. Thelight-emitting device according to claim 1, wherein the number of thefirst opening is more than one, and the first openings are arranged in atwo-dimensional array in the current blocking layer and separated fromone another.
 13. The light-emitting device according to claim 12,wherein the current blocking layer is a contiguous layer.
 14. Thelight-emitting device according to claim 12, wherein the number of thesecond opening is more than one, and the second openings are arranged ina two-dimensional array in the electrode and separated from one another,and each of the second openings is correspondingly formed within one ofthe first openings.
 15. The light-emitting device according to claim 14,wherein the electrode is a contiguous layer.
 16. The light-emittingdevice according to claim 1, wherein the electrode covers a side wall ofthe current blocking layer enclosing the first opening.
 17. Thelight-emitting device according to claim 16, wherein the electrodecovers more than 50% of a surface area of the current blocking layer.18. The light-emitting device according to claim 1, wherein theelectrode is separated from a side wall of the current blocking layerenclosing the first opening.
 19. The light-emitting device according toclaim 18, wherein the electrode covers less than 50% of a surface areaof the current blocking layer.
 20. The light-emitting device accordingto claim 1, wherein the current blocking layer has a thicknesssubstantially equals to n λ/4, wherein λ is the peak wavelength of theradiation emitted from the light-emitting stack, and n is an oddpositive integer.